1. Field of the Invention
This invention pertains to a roll mill, and in particular to a flaking mill for milling particulate material having at least two rollers that are pressed against one another by means of a pressure device, with each of the axial ends of the rollers having a product channel arranged relative thereto, with an inclined guide surface thereof being adapted to bring the product to be milled, Which tends to extend beyond the axial length of the rollers, back to the converging gap of the rollers.
2. Discussion of the Background of the Invention and Material Information
U.S. Pat. No. 4,905,917 and cognate European Patent EP 0271828, also assigned to the assignee of the present invention, discloses a roll mill in which product guides or guide channels are utilized on both ends or edges of the rolls which serve to return the product to be milled, that flows outwardly towards the ends of the rolls, back into the grinding gap.
In addition it is known that the product that is fed into the grinding gap, respectively the converging gap or nip between the rolls, which is not directly pulled into the gap, has a tendency to flow toward the ends of the rolls, so that predominately clumps and coarse particles etc. in the product, which are in a granulatory manner substantially larger than the product itself, and therefore cannot be gripped by the grinding nip, according to the noted tendency, arrive at the ends of the rolls.
Roll mills, which were already the state of the art with reference to prior art U.S. Pat. No. 4,905,917, were so constructed that the roll ends had no frusto-conical tapered or bevelled ends so that the side edges or surfaces of the rolls closely adjoined the side edges of the roll mill, so that the product could flow up to the side edges of the roll mill, with the result that the noted clumps or other coarse particles were kept in motion at the roll ends until they were worn down to size which permitted entry into the grinding gap. At the time of such entry, these particles are however still larger than the granulations of the product, that is the deformation forces are greater, which is also the case with the surface loading upon the rolls. Such loads can cause damage to rolls, particularly when this condition occurs at the roll edges. This results in break out portions at the roll ends or edges.
In order to at least partially avoid the resulting differing grinding conditions, it was already suggested in U.S. Pat. No. 4,905,917 to provide a frusto-conical taper at the roll ends, on which a guide surface adjoins that prohibits that the noted coarse parts can bypass the rolls, via the channel formed by the taper at the ends of the rolls, without being milled.
While these tapers or chamfers have the advantage that while the noted clumps or other coarse particles remain in this area without damaging the rolls, it is however a disadvantage that the material flow is disturbed.